Reduction of Cr(VI) by Urea-Dispersed Nanoscale Zero-Valent Iron

Urea was used to disperse nanoscale zero-valent iron (NZVI) for reduction of Cr(VI) to Cr(III) in aqueous solution. Scanning electron microscope and fourier transform-infrared spectra investigations demonstrated that urea could effectively increase the dispersion of NZVI resulting in more effective reduction sites (ERS) for Cr(VI) ions. Batch reduction experiments indicated that the reductive capacity of urea dispersed NZVI (UNZVI) was significantly improved, as the reductive efficiency reached 96.8% under optimal condition compared with the raw NZVI (72.14%). Additionally, the NZVI was stable for at least 28 days after urea treatment. The dispersion mechanism was proposed that the steric hindrance effect of the urea coating on the surface might play a key role in dispersing the NZVI particles.